Radiation Beam Analyzer And Method

ABSTRACT

A radiation beam analyzer for measuring the distribution and intensity of radiation produced by a Cyberknife®. The analyzer employs a relative small tank of water into which a sensor is placed to maintain a constant SAD (source to axis distance). A first method maintains a fixed position of detector, and raises or lowers the small tank of water. A second method moves the detector up, down or rotationally synchronously in opposite directions with respect to the small tank of water to keep the SAD constant. These methods position the detector relative to the radiation source to simulate the location of a malady within a patient&#39;s body. An embodiment of the present invention enables measurements of substantially larger fields. This is accomplished by rotating a tank of water 90 degrees from a first position to a second position

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 13/174,950, filed Jul. 1, 2011, entitled “Radiation BeamAnalyzer and Method”, which is a continuation-in-part of U.S. patentapplication Ser. No. 13/018,869, filed Feb. 1, 2011, entitled “RadiationBeam Analyzer and Method”, which is a continuation of U.S. patentapplication Ser. No. 12/630,450, filed Dec. 3, 2009, entitled “RadiationBeam Analyzer and Method,” now U.S. Pat. No. 7,902,515, whichapplication claims the benefit under 35 U.S.C. 119(e) of U.S.Provisional Patent Application Nos. 61/119,629, filed Dec. 3, 2008,entitled, “Cyberknife® Radiation Beam Analyzer and Method” and61/141,751, filed Dec. 31, 2008, entitled, “Isocentric Radiation BeamAnalyzer and Method”. This application is also related to U.S. PatentApplication No. 61/083,740, filed Jul. 25, 2008, entitled, “ModularRadiation Beam Analyzer Software”; U.S. patent application Ser. No.11/510,275, filed Aug. 25, 2006, entitled, “Convertible Radiation BeamAnalyzer System”; U.S. Pat. No. 7,193,220, issued Mar. 20, 2007,entitled, “Modular Radiation Beam Analyzer”; and U.S. Pat. No.6,225,622, issued May 1, 2001, entitled “Dynamic Radiation ScanningDevice.” The entirety of these patent applications and patents arehereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates to a method and device for measuring theradiation dose of a linear accelerator or other radiation producingdevice at a target, and particularly relates to the tracking andmeasurement of a radiation dose from a Cyberknife®, a linear acceleratoror other radiation producing devices used in conjunction with aradiosurgery system for the non-invasive treatment of both cancerous andnon-cancerous tumors anywhere in the human body including the prostrate,lung, brain, spine, liver, pancreas and kidney.

BACKGROUND OF THE INVENTION

Various well known medical techniques for the treatment of malignanciesinvolve the use of radiation. Radiation sources, for example medicallinear accelerators, are typically used to generate radiation which isdirected to a specific target area of a patient. Proper doses ofradiation directed at the malignant area of the patient are of theupmost importance. When properly applied, the radiation produces anionizing effect on the malignant tissues of the patient, therebydestroying the malignant cells. As long as the dosimetry of the appliedradiation is properly monitored, the malignancy can be treated withoutany detriment to the surrounding healthy body tissue. The goal of thesetreatments is to focus a high dose of radiation to a tumor or malignantcells while minimizing the exposure of the surrounding healthy tissue tothe radiation. Accelerators may be utilized to deliver the radiation.Different accelerators have varying characteristics and output levels.The most common type of accelerator produces pulse radiation. The outputbeam has a rectangular shape in cross section and a cross sectional areatypically between 1 and 1,600 square centimeters (cm²). Preferably, thecross sectional area or field size is between 1×1 square centimeters(cm²) and 40×40 square centimeters (cm²). Rectangular or square crosssectional shapes are often changed to any desired cross sectional shapeusing molded or cast lead or cerrobend materials. More advancedaccelerators use multi-leaf collimators. Other accelerators arecontinuously or non-pulsed, such as cobalt radiation machines. Someaccelerators utilize a swept electron beam, which passes a very narrowelectron beam across the treatment field by means of varyingelectromagnetic fields.

To ensure proper dosimetry, linear accelerators used for the treatmentof malignancies must be calibrated. Both the electron and photonradiation must be appropriately measured and correlated to theparticular device. The skilled practitioner must insure that both theintensity and duration of the radiation treatment is carefullycalculated and administered so as to produce the therapeutic resultdesired while maintaining the safety of the patient. Parameters such asflatness, symmetry, radiation and light field alignment are typicallydetermined. The use of too much radiation may, in fact, cause sideeffects and allow destructive effects to occur to the surroundingtissue. Use of an insufficient amount of radiation will not deliver adose that is effective to eradicate the malignancy. Thus, it isimportant to be able to determine the exact amount of radiation thatwill be produced by a particular machine and the manner in which thatradiation will be distributed within the patient's body.

In order to produce an accurate assessment of the radiation received bythe patient, at the target area, some type of pattern or map of theradiation at varying positions within the patient's body must beproduced. These profiles correlate: 1) the variation of dose with depthin water generating percent depth dose profiles, 2) the variation ofdose across a plane perpendicular to the radiation source generating thecross beam profiles, and 3) the variation of dose with depth in watergenerating percent depth dose and TMR/TPR (Tissue Maximum Ratio/TissuePhantom Ratio) when the SAD (source to axis distance) is constantprofiles. These particular measurements of cross beam profiles are ofparticular concern in the present invention. Although useful for otheranalyses, the alignment of the cross profiles in both radial andtransverse planes are the basis of the present invention.

There are companies that provide the calibration service to hospitalsand treatment centers. These physicists must visit the facility andconduct the calibration of the radiation source with their ownequipment. This requires lightweight, easily portable, less cumbersomeradiation measuring devices that can be quickly assembled anddisassembled on site. The actual scanning should also be expeditiouswith the results available within a short time frame. Such equipmentallows a physicist to be more efficient and calibrate more radiationdevices in a shorter period of time.

One existing system for measuring the radiation that is produced bymedical linear accelerators utilizes a large tank on the order of 50cm×50 cm×50 cm filled with water. A group of computer controlled motorsmove the radiation detector through a series of pre-programmed stepsalong a single axis beneath the water's surface. Since the density ofthe human body closely approximates that of water, the water-filled tankprovides an appropriate medium for creating a simulation of both thedistribution and the intensity of radiation which would likely occurwithin the patient's body. The aforementioned tank is commonly referredto as a water phantom. The radiation produced by the linear acceleratorwill be directed into the water in the phantom tank, at which point theintensity of the radiation at varying depths and positions within thewater can be measured with the radiation detector. As the radiationpenetrates the water, the direct or primary beam is scattered by thewater, in much the same way as a radiation beam impinging upon the humanpatient. Both the scattered radiation, as well as the primary radiation,are detected by the ion-chamber, which is part of the radiation detectoror by radiation sensitive diodes.

The ion-chamber is essentially an open air capacitor which produces anelectrical current that corresponds to the number of ions producedwithin its volume. The detector is lowered to a measurement point withinthe phantom tank and measurements are taken over a particular timeperiod. The detector can then be moved to another measurement pointwhere measurements are taken as the detector is held in the secondposition. At each measuring point a statistically significant number ofsamples are taken while the detector is held stationary.

In radiation therapy and radiosurgery, for example, a tumor may benon-invasively destroyed by a beam of ionizing radiation that kills thecells in the tumor. It is desirable to direct the radiation beam only tothe tumor and not to the healthy tissue which surrounds the tumor.Therefore, accurate aiming of the beam at the tumor is extremelyimportant in these radiation treatments. The goal is to focus a highdose of radiation to the tumor while minimizing the exposure of thesurrounding healthy tissue to radiation. For adequate distribution ofradiation dosage to the tumor, the direction of the radiation beam istypically adjusted during the treatment to track the tumor.

The most advanced modern radiosurgery systems, such as the Cyberknife®Robotic Radiosurgery System of Accuray, Inc., utilizes stereo onlinex-ray imaging during treatment to enhance the accuracy of the radiationtreatment. The position of a patient's bony landmarks, e.g. their skull,can be determined with high accuracy by using the Cyberknife® stereox-ray camera system. Thus, this highly accurate x-ray camera system canbe used to treat a target region if the position of the target regionrelative to a bony landmark remains constant. However, the x-ray camerasystem cannot be used to determine the position of a target region ifthe position of the target region relative to a bony landmark changesbecause the target, e.g. a tumor, is generally not visible in x-rayimages. For example, a target region in a patient's abdomen or chestcannot be treated with this method alone.

An image guidance system is essential to the proper operation of theCyberknife® system. The first method developed for controlling the imageguidance system was known as 6D or skull based tracking. An X-ray cameraproduces images which are compared to a library of computer generatedimages of the patient anatomy Digitally Reconstructed Radiographs(DRR's), and a computer algorithm determines what motion correctionshave to be given to the robot because of patient movement. This imagingsystem allows the Cyberknife® to deliver radiation with an accuracy of0.5 mm without using mechanical clamps attached to the patient's skull.The use of the image guided technique is referred to as framelessstereotactic radiosurgery. This method is referred to as 6D becausecorrections are made for the 3 translational motions (X, Y and Z) andthree rotational motions.

DESCRIPTION OF THE PRIOR ART

Several prior art devices are known to teach systems for ascertainingthe suitable dosimetry of a particular accelerator along with methodsfor their use. U.S. Pat. Nos. 5,621,214 and 5,627,367, issued toSofield, are directed to a radiation beam scanner system which employs apeak detection methodology. The device includes a single axis mountedwithin a water phantom. In use, the water phantom must be leveled and areference detector remains stationary at some point within the beamwhile the signal detector is moved up and down along the single axis bythe use of electrical stepper motors. While these devices employ a waterphantom, they are limited to moving the signal detector along the singleaxis and can only provide a planar scan of the beam.

U.S. Patent Application Publication 2006/0033044 A1, to Gentry et al.,is directed to a treatment planning tool for multi-energy electron beamradiotherapy. The system consists of a stand-alone calculator thatenables multi-energy electron beam treatments with standard singleelectron beam radio-therapy equipment thereby providing improved doseprofiles. By employing user defined depth-dose profiles, the calculatormay work with a wide variety of existing standard electron beamradiotherapy systems.

U.S. Pat. No. 6,225,622, issued May 1, 2001, to Navarro, the inventorherein, describes a dynamic radiation measuring device that moves theion chamber through a stationary radiation beam to gather readings ofradiation intensity at various points within the area of the beam. Thedisclosure of this patent is incorporated herein, by reference.

U.S. Pat. No. 4,988,866, issued Jan. 29, 1991, to Westerlund, isdirected toward a measuring device for checking radiation fields fromtreatment machines used for radiotherapy. This device comprises ameasuring block that contains radiation detectors arranged beneath acover plate, and is provided with field marking lines and an energyfilter. The detectors are connected to a read-out unit for signalprocessing and presentation of measurement values. The dose monitoringcalibration detectors are fixed in a particular geometric pattern todetermine homogeneity of the radiation field. In use, the measuringdevice is able to simultaneously check the totality of radiation emittedby a single source of radiation at stationary positions within themeasuring block.

U.S. Pat. No. 7,189,975, issued to Schmidt et al., is directed to a wirefree, dual mode calibration instrument for high energy therapeuticradiation. The apparatus includes a housing with opposed first andsecond faces holding a set of detectors between the first and secondfaces. A first calibrating material for electrons is positioned tointercept electrons passing through the first face to the detectors, anda second calibrating material for photons is positioned to interceptphotons passing through the second face to those detectors.

These devices do not use a water phantom and are additionally limited inthat all of the ionization detectors are in one plane. This does notyield an appropriate three-dimensional assessment of the combination ofscattering and direct radiation which would normally impinge the humanbody undergoing radiation treatment. Thus, accurate dosimetry in areal-life scenario could not be readily ascertained by the use of thesedevices.

U.S. Pat. No. 5,006,714, issued Apr. 9, 1991, to Attix, utilizes aparticular type of scintillator dosimetry probe which does not measureradiation directly, but instead measures the proportional light outputof a radiation source. The probe is set into a polymer material thatapproximates water or muscle tissue in atomic number and electrondensity. Attix indicates that the use of such a detector minimizesperturbations in a phantom water tank.

Additionally, there is an apparatus called a Wellhofer bottle-ship whichutilizes a smaller volume of water than the conventional water phantom.The Wellhofer device utilizes a timing belt and motor combination tomove the detector through the water, thus requiring a long initialset-up time.

Thus, there exists a need for a portable, modular radiation beammeasuring device. The device should be capable of rapid assembly anddisassembly for use at various locations to calibrate variousCyberknife® systems. The device should be capable of repeatable,accurate detection of the radiation emitted from the Cyberknife®. Sincethe distance between the Cyberknife® and the item being treated, e.g. atumor, remains constant with this system, the device should also utilizea relative small volume of water or other fluid.

None of the above prior art devices are capable of performing fast andaccurate isocentric measurements that result in direct measurement ofthe TMR/TPR (Tissue Maximum Ratio/Tissue Phantom Ratio) in depth andiscoentric cross profiles. There also exists a need for a portable,modular radiation beam measuring device. The device should be capable ofrapid assembly and disassembly for use at various locations to calibratevarious iscoentric radiation beam systems. The device should be capableof repeatable, accurate detection of the radiation emitted from theradiation source. Since the distance between the iscoentric radiationbeam source and the item being treated, e.g. a tumor, remains constantwith this system, the device should also be capable of utilizing arelative small volume of water. Additionally, in the radiation treatmentplanning currently employed, the input sent to the radiation treatmentplanning computerized system is from non-isocentric data (SSD) which isthen converted to isocentric data (SAD). This presents two majorproblems. First, the conversion algorithms used for the conversion arecomplicated. Second, the results are inaccurate. Thus, there is a needfor a quick and accurate device to perform isocentric measurements forradiation treatment planning.

SUMMARY OF THE INVENTION

A first embodiment of the invention embodies a radiation beam analyzerfor measuring the distribution and intensity of radiation produced bythe Cyberknife® or other radiation producing machine. The analyzeremploys a relatively small tank of water into which a sensor is placed.The distance between the sensor and the radiation source is not varied.The tank of water is raised and lowered relative to the sensor tosimulate the location of a malady within a patient's body. This movementof the tank permits the radiation from the Cyberknife®, or otherradiation producing machine, to be properly calibrated and adjusted fora proper treatment of a malady in a patient.

Another embodiment of the invention embodies a radiation beam analyzerfor measuring the distribution and intensity of radiation produced by aradiation source. The analyzer employs a relatively small tank of waterinto which a sensor or detector is placed. The distance between thesensor and the radiation source is not varied. There are two methods tomaintain the SAD (source to axis distance) constant. A first methodmaintains the position of detector fixed, utilizing a holder designed toretain the detector, and raises or lowers the small tank of water. Asecond method moves the detector up or down with a raising and loweringmechanism in one direction and synchronically moves the small tank ofwater in the opposite direction with another raising and loweringmechanism. The second method also keeps the SAD constant. These methodsposition the detector relative to the radiation source to simulate thelocation of a malady within a patient's body. This movement of the tankpermits the radiation from the iscoentric radiation beam source to beproperly isocentrically measured.

A third embodiment of the present invention enables measurements ofsubstantially larger fields than the first two embodiments. This isaccomplished by rotating the tank up to 90 degrees from a first positionto a second position.

Accordingly, it is an objective of the present invention to provide anaccurate measurement of the radiation from a linear accelerator or theCyberknife® used to perform radiosurgery or to treat a malady.

It is a further objective of the present invention to accuratelyposition a linear accelerator or the Cyberknife® relatively to a maladyin a patient's body.

It is yet another objective of the present invention to provide amodular radiation device including a relatively small tank of waterwhich is moved relative to a fixed sensor in order to determine theproper amount of radiation required to treat a malady.

It is a still further objective of the present invention to provide asystem and method for electronically controlling the movement of a tankof water and the measurement of radiation from a Cyberknife®.

It is a still further objective of the present invention to provide amechanism to rotate a tank of water to enable accurate positioning of alinear accelerator.

It is a still further objective of the present invention to provide amechanism to rotate a treatment table on which a patient is resting toenable accurate positioning of a linear accelerator.

It is a further objective of the present invention to accuratelyposition the radiation detector, as well as obtain high repeatability ofthe measurements.

It is yet another objective of the present invention to provide amodular radiation device including a relatively small tank of waterwhich is moved relative to a fixed detector or sensor in order todetermine the proper amount of radiation required to treat a malady.

It is a still further objective of the present invention to provide asystem and method for electronically controlling the movement of arelatively small tank of water and the movement of a detector or sensormounted within the tank for the measurement of radiation from aniscoentric radiation beam source.

It is still yet another objective of the present invention to provide asystem wherein relative beam radiation data from 0.4 cm to 40 cm can bescanned and analyzed.

It is still a further objective of the present invention to provide asystem having a modular design which can be applied to a 1-D(imensional), 2-D and 3-D systems.

Other objects and advantages of this invention will become apparent fromthe following description taken in conjunction with any accompanyingdrawings wherein are set forth, by way of illustration and example,certain embodiments of this invention. Any drawings contained hereinconstitute a part of this specification and include exemplaryembodiments of the present invention and illustrate various objects andfeatures thereof.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of one embodiment of the present inventionin use measuring the radiation from a Cyberknife®;

FIG. 2 is a front view of one embodiment of the present invention;

FIG. 3 is a side view of one embodiment of the present invention;

FIG. 4 is a top perspective view of one embodiment of the presentinvention;

FIG. 5 is an enlarged front view of one embodiment of the presentinvention;

FIG. 6 is an enlarged front perspective view of one embodiment of themeasurement tank of the present invention;

FIG. 7 is a perspective view of the prior art radiation treatment systemutilizing an iscoentric radiation beam source to treat a patient;

FIG. 8 is a front view of one embodiment of the present inventionincorporating the small tank with the detector in a raised position;

FIG. 9 is a front view of one embodiment of the present inventionincorporating the small tank with the sensor in a lowered position;

FIG. 10 is a side view of one embodiment of the present inventionincorporating the small tank with the detector in a raised position;

FIG. 11 is a side view of the small tank of one embodiment of thepresent invention with the detector in a raised position;

FIG. 12 is a side view of the small tank of one embodiment of thepresent invention with the detector in a lowered position;

FIG. 13 is a rear perspective view of the small tank of one embodimentof the present invention with the detector in a raised position;

FIG. 14 is a rear perspective view of the small tank of one embodimentof the present invention with the detector in a lowered position;

FIG. 15 is a perspective view of one embodiment of the present inventionin use measuring the radiation from an iscoentric radiation beam source;

FIGS. 16A and 16B are the results of an iscocentric depth scan (TPR) anda cross profile;

FIG. 17 is a perspective view of one embodiment of the presentinvention; and

FIG. 18 is a perspective view of one embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

While the present invention is susceptible of embodiment in variousforms, there is shown in the drawings and will hereinafter be describeda presently preferred, albeit not limiting, embodiment with theunderstanding that the present disclosure is to be considered anexemplification of the present invention and is not intended to limitthe invention to the specific embodiments illustrated.

The present invention is designed to measure with accuracy, precisionand speed the radiation beams produced by a Cyberknife® or otherradiation producing device. The Dynamic Phantom and Direct TMP/TPRDirect Measurement of radiation from a device utilized in radiosurgeryhave been previously described in applicant's related patentapplications referred to herein. A combination of these two measurementmethods and modifications of some of the features of these measurementmethods has resulted in the present invention which will be describedhereinafter.

Although the two basic concepts of Dynamic Phantom and Direct TMR/TPRDirect measurements are the same, the present invention requires water,not solid water like the Dynamic Phantom and is different from TMR/TPR.The radiation is imparted with the radiation source on the top of atank, not laterally like in applicant's previous TMR/TPR measurements.

The present invention also permits the use of a tank with asignificantly smaller capacity. In a preferred embodiment of the presentinvention, the tank's capacity is 2.5 liters versus a prior art tank'scapacity of 100 liters.

Referring to FIGS. 1-6, a first embodiment of the invention including amodular radiation beam analyzer 10 for measuring the distribution andintensity of radiation produced by a Cyberknife® 12 in a radiosurgerysystem is illustrated. A radiation beam 14 is emitted by a Cyberknife®in a substantially vertical direction. The beam 14 is very sharp and canbe positioned on a patient with accuracy of less than one millimeter.The beam 14 is used to treat areas on a patient which preferably have aminimum field size of 0.5 cm in diameter and a maximum field size of 6cm in diameter. The radiosurgery system, in which the Cyberknife® isemployed, requires that all the radiation measurements be takenutilizing the isocentric method or direct measurement of TMR/TPR (TissueMaximum Ratio/Tissue Phantom Ratio). In addition, because of theaccuracy of this radiosurgery procedure, the measurements of theradiation require extreme accuracy.

The relatively small tank of the present invention is placed onto acarriage 18 of a measurement device which employs a substantially largertank 30. The larger measurement device allows the carriage 18 to bemoved in three different axes, X, Y and Z. The X axis extends along ahorizontal portion of the tank 30 and can be seen in FIG. 2. The Y axisextends in the vertical direction and can also be seen in FIG. 2. The Zaxis extends toward and away from a rear wall of the tank 30 and can beseen in FIG. 3. Small motors, such as a stepper motor, move the carriage18 along all three axes. The present invention includes a second tank 16that is movable in the Y direction only. While a stepper motor is apreferred embodiment, any type of motor or device which can move thecarriage 18 along each of the three axes can be utilized.

In radiosurgery systems which utilize the Cyberknife®, the distancebetween the Cyberknife® and the malady being treated on a patient, suchas a tumor, remains constant. Thus, in order to simulate the differentpositions or depths in a patient's body that the tumor or other maladybeing treated may be located, only the relative depth of the water,which simulates the depth of the item within a patient's body, needs tobe varied. Once the correct depth or position within a patient's body issimulated by moving a sensor 32 to a specific depth in the water withinthe second tank 16 the amount of radiation from the Cyberknife® can beregulated to properly treat the tumor or malady. The present inventionaccomplishes this by moving the second tank 16 vertically up and downalong the Y axis. This is illustrated in FIGS. 1-6.

The sensor 32 is mounted on or positioned within a support 34, FIGS. 4,5 and 6. The support 34 is secured onto a substantially vertical rod orsupport 36. The support 36 is in turn connected to and supported on asubstantially horizontal rod or support 38. While a preferred connectiondevice 40 is illustrated which applies a transverse force on supports 36and 38, any other type of connection device 40 could also be employed.Support or rod 38 is connected to a guideway 42, FIG. 3, utilizing aconnection device 44 mounted on the guideway. The support 34 permits thedistance between the Cyberknife® 12 and the sensor 32 to be adjusted tosimulate the distance between a commercial Cyberknife® and the maladybeing treated. The supports 38 and 34 permit the sensor 32 to be alignedwith the radiation beam 14 from the CyberKnife® 12.

A stepper motor or other similar device 19 (FIG. 8) moves the carriage18 along the X axis. A stepper motor or other similar device 21 (FIG. 4)moves the carriage 18 along the Y axis. This simulates the depth orlevel into which a malady is located within a patient's body. A steppermotor or other similar device 45 (FIG. 3) moves the carriage 18 alongthe Z axis. The carriage 18 has a support plate or platform 44 securedthereon, FIG. 5. The lower portion of second tank 16 is removablysecured to the platform 44 so that the tank will not fall off thecarriage 18 during operation of the present invention. There are variousmethods of securing second tank 16 to platform 44 including but notlimited to fastening, gluing, welding, etc. While in the preferredembodiment, the second tank 16 is releasably secured to platform 44; itcould also be permanently attached thereto.

While the second tank 16 is illustrated as substantially square in crosssection and rectangular in height, a preferred embodiment iscylindrical. The cylinder is preferably 19 cm in diameter and 40 cmhigh. It is made from a clear acrylic material. Tanks having variousother dimensions and weights can also be utilized. Tanks can also bemade from various other materials.

This embodiment of the present invention utilizes the software andprogramming of applicant's U.S. patent application Ser. No. 61/083,740,filed Jul. 25, 2008, entitled, “Modular Radiation Beam AnalyzerSoftware” and U.S. patent application Ser. No. 11/510,275, filed Aug.25, 2006, entitled, “Convertible Radiation Beam Analyzer System” tocontrol the motors which operate the guideways, to acquire data, toanalyze the data, to provide graphical representations of the data andto transfer data with the pertinent modifications.

This embodiment of the present invention can be used with a single or anarray of ion chambers. It can also be used with a plurality of diodes.The present invention can also be utilized with conventional radiationtherapy. When used with conventional radiation therapy the dimensions ofthe second tank 16 are 14 cm long by 14 cm wide by 40 cm high.

Another embodiment of the present invention is designed toisocentrically measure with accuracy, precision and speed the radiationbeams produced by a radiation beam source. This second embodiment of thepresent invention can also be used with a Cyberknife® radiation system.The dynamic phantom measurement of radiation and direct measurement ofTMR/TPR (Tissue Maximum Ratio/Tissue Phantom Ratio) functions from adevice utilized in radiosurgery have been previously described inapplicant's related patent applications referred to herein. Acombination of these two measurement methods and modifications of someof the features of these measurement methods has resulted in the presentinvention which will be described hereinafter. An iscoentric radiationtreatment system maintains the distance between the radiation source andthe malady of a patient constant. In other words the SAD (source to axisdistance) is constant. The radiation source can also be pivoted aroundthe patient utilizing a manipulator 116 as illustrated in FIGS. 7 and15.

There are two methods to maintain the SAD (source to axis distance)constant. A first method maintains the position of detector fixed;utilizing a holder designed to retain the detector, and raises or lowersthe small tank of water, as illustrated in FIGS. 1-6, 8, and 9. A secondmethod moves the detector up or down with a raising and loweringmechanism in one direction and synchronically moves the small secondtank of water in the opposite direction with another raising andlowering mechanism, as illustrated in FIGS. 10-14. The second methodalso keeps the SAD constant. These methods position the detectorrelative to the radiation source to simulate the location of a maladywithin a patient's body. This movement of the tank permits the radiationfrom the radiation beam source to be properly isocentrically measured.

Although the two basic concepts of dynamic phantom measurement anddirect measurement of TMR/TPR functions are the same, this embodiment ofthe present invention can use water instead of solid water like thedynamic phantom measurement to measure cross beam profiles. This secondembodiment of the present invention can also perform direct measurementsof TMR/TPR with the radiation being imparted from source on the top of atank, not laterally like in applicant's previous TMR/TPR measurements.Finally, combining these two concepts it is possible with a singledevice to isocentrically measure relative depth dose (TMR/TPR) and crossbeam profiles. With the previous inventions two different devices wererequired. This second embodiment of the present invention also permitsthe use of a tank of water with a significantly smaller capacity thanemployed in prior art measurement systems. In a preferred embodiment thetank's capacity is 2.5 liters versus a prior art tank's capacity of 100liters.

Referring now to FIGS. 7 and 15, a prior art iscoentric radiationtreatment apparatus 110 is illustrated in FIG. 7. The iscoentricradiation treatment apparatus illustrated in FIG. 7 comprises aradiation generation unit 112, a variable collimator 114, a manipulator116, a movable treatment table 118, a diagnosis imager 120, and acontrol unit 122 which produces a radiation beam 124. The modularradiation beam analyzer 126 of the present invention for measuring thedistribution and intensity of radiation produced by an iscoentricradiation beam 124 in a radiosurgery system is illustrated in FIG. 15.The radiation beam 124 is emitted by an iscoentric radiation beam sourcein a substantially vertical direction. The radiation beam 124 is verysharp and can be positioned on a patient with accuracy of less that onemillimeter. The beam 124 is used to treat areas on a patient whichpreferably have a minimum field size of 0.5 cm in diameter and a maximumfield size of 6 cm in diameter. The radiosurgery system, in which theiscoentric radiation beam is employed, requires that all the radiationmeasurements be taken utilizing the isocentric method of directmeasurement of TMR/TPR (Tissue Maximum Ratio/Tissue Phantom Ratio) ofthe present invention. In addition, because of the accuracy of thisradiosurgery procedure, the measurements of the radiation delivered tothe patient require extreme accuracy.

The relatively small tank 128 of this second embodiment of the presentinvention is placed onto a carriage 130 of a measurement device. Aportable folding frame 131 (FIGS. 8 and 9) holds the whole system. Themodular radiation beam analyzer 126 enables the carriage 130 to be movedin three different axes, X, Y and Z. The X axis extends in a horizontaldirection along a portion of the tank 132 and is illustrated in FIGS. 8and 15. The Z axis extends in a vertical direction and can also be seenin FIGS. 8 and 15. The Y axis extends toward and away from a rear wallof tank 132 and can be seen in FIGS. 4 and 9. Small motors, such as astepper, servo or digital motor, move the carriage 130 along all threeaxes. While a stepper motor is a preferred embodiment, any type of motoror device which can move the carriage 139 alone each of the three axescan be utilized.

This second embodiment of the present invention includes a small tank128 which is movable in the Z direction by motor 127 (FIG. 10) and adetector or sensor 134 which is movable in the Z direction also. A smallmotor, such as a stepper motor 136, rotates a screw 138 in both aclockwise and counter clockwise direction, as illustrated in FIGS. 11and 12. A mounting support 140 holds and retains the detector or sensor134 in a fixed position. The mounting support 140 is secured to andsupported on the screw 138 such that when the screw rotates in onedirection the mounting support 140 will be raised, relative to thebottom of the tank 132, and when the screw is rotated in the oppositedirection the screw will be lowered. While a preferred mounting support140 is illustrated which applies a transverse force on detector orsensor 134, any other type of mounting support 140 could also beemployed. The mounting support 140 permits the distance between theiscoentric radiation beam source 112 and the detector or sensor 134 tobe adjusted to simulate the distance between a commercial iscoentricradiation beam and the malady of an individual or patient to be treatedutilizing the radiosurgery system described above. The mounting support140 also permits the detector or sensor 134 to be aligned with theradiation beam 124 from the iscoentric radiation beam source 112.

In radiosurgery systems which utilize the iscoentric radiation beam, thedistance between the iscoentric radiation beam source 112 and the maladybeing treated on a patient, such as a tumor, remains constant. Thus, inorder to simulate the different positions or depths in a patient's bodythat the tumor or other malady being treated may be located, only therelative depth of the water, which simulates the depth of the itemwithin a patient's body, needs to be varied. Once the correct depth orposition within a patient's body is simulated by moving detector orsensor 134 to a specific depth in the water within the tank 128, theamount of radiation from the radiation beam source can be regulated toproperly treat the tumor or malady. This second embodiment of thepresent invention accomplishes this by utilizing one of three methods.The first method maintains the position of detector 134 fixed, utilizinga mounting support 140 designed to retain the detector, and raises orlowers the small tank of water 128. The second method moves the detectoror sensor 134 up or down with a raising and lowering mechanism in onedirection and synchronically moves the small tank of water in theopposite direction with another raising and lowering mechanism. Thesecond method also keeps the SAD constant. These methods position thedetector relative to the radiation source to simulate the location of amalady within a patient's body. This movement of the tank permits theradiation from the iscoentric radiation beam source to be properlyisocentrically measured. Main difference between the three methods: thesecond method uses an extra motor, extending the scanning capability tothree (3) axes X, Y, Z, therefore scanning in depth, and radialtransverse and diagonal directions. The third method utilizes thetreatment table to provide controlled rotation to the testing device toextend the scanning capability to three axes. The first method can scanonly in depth and transverse directions. When two of the motors aresimultaneously operated, the object being moved by these motors, thecarriage 18 and/or the second tank 16, is/are moved is a directionbetween or diagonal to the two axes of movement of the object. Forexample, the X and Y axes, the X and Z axes, the Y and Z axes. As anexample, if the motor 19 moves an object along the X axis and motor 21moves the object along the Y axis, then when motors 19 and 21 areoperated simultaneously the object moves on a diagonal between the X andY axes. Also, motor 45 moves an object along the Z axis, so that whenmotor 45 and motor 21 are operated simultaneously the object movesbetween the Z and Y axes. Finally, motor 45 moves an object along the Zaxis, so that when motor 45 and motor 19 are operated simultaneously theobject moves between the Z and X axes.

The first method raises and/or lowers the tank of water 128 by raisingand/or lowering the carriage 130 with stepper motors or similar devicescapable of raising and/or lowering the carriage. The second methodraises and/or lowers the detector or sensor 134 by raising and/orlowering the mounting support 140 utilizing a screw mechanism 138 andstepper motor 136 or similar device which can raise and/or lower thesupport. Simultaneously the tank 128 is raised and/or lowered by raisingand/or lowering the carriage 130 as described herein above. The motor(s)or device(s) which raise and/or lower the mounting support 140 and themotor(s) or device(s) which raise and/or lower the carriage 130 aresynchronized to maintain the detector or sensor 134 in a fixed positionrelative to the radiation source. In other words to keep the SADconstant.

As illustrated, tank 128 is 8 cm long, 8 cm wide and 40 cm high. It hasa capacity of 2.5 liters. It is made from a clear acrylic material. In apreferred embodiment, the tank 128 is cylindrical having a diameter of19 cm and a height of 40 cm. Tanks having various other dimensions andweights can also be utilized. Tanks can also be made from various othermaterials.

A wire or cable 142 extends from the detector or sensor to a recordingdevice to measure and record the amount of radiation delivered to aspecific point by the radiation source. Another wire or cable 144extends from a control box 146, FIG. 9. The control box controls themovement of the carriage 130 in the X, Y and Z directions. Another wireor cable 148 extends from the motor 136 to a control device 150. Thiscontrol device 150 synchronizes the movement between the carriage 130and the mounting support 140 to maintain the detector or sensor in aposition fixed relative to the radiation source.

This embodiment of the present invention utilizes the software andprogramming of applicant's U.S. patent application Ser. No. 61/083,740,filed Jul. 25, 2008, entitled, “Modular Radiation Beam AnalyzerSoftware” and U.S. patent application Ser. No. 11/510,275, filed Aug.25, 2006, entitled, “Convertible Radiation Beam Analyzer System” tocontrol the motors which operate the guideways, to acquire data, toanalyze the data, to provide graphical representations of the data andto transfer data with the pertinent modifications.

This embodiment of the present invention can be used with a single or anarray of ion chambers. It can also be used with a single or an array ofdiodes. This embodiment of the present invention can also be utilizedwith Cyberknife® or conventional radiation therapy. When used withconventional radiation therapy, the dimensions of the tank 128 are 14 cmlong by 14 cm wide by 40 cm high. But the main applications aremeasurements of small fields, like the ones used in Cyberknife® machinesand stereotactic procedures.

When scanning in the Z direction, the iscocentric scanning generates theTMR/TPR function. This is accomplished using either one of the twomethods described herein before. This is different from a conventionalscanner which does not keep the SAD constant and generates a PDD(percentage depth dose) function. It should also be noted that TMR(Tissue Maximum Ratio) cannot scan across profiles isocentrically. It isfurther noted that dynamic phantom measurements cannot scan depthsisocentrically. Results of an iscocentric depth scan (TMR) and crossprofiles are illustrated in FIGS. 16A and 16B.

Referring to FIG. 17, a third embodiment of the present invention willnow be described. This third embodiment operates and is used in the samemanner as the first two embodiments of the invention to perform directmeasurements of TMP/TPR_SAD (equivalent to isocentric measurements) withthe radiation being imparted from a source (not shown) on the top of thetank 228. The radiation source could be the same as 12 and 112,illustrated in FIGS. 1 and 7 respectively. A tank 228 which contains aphantom body of water is mounted onto a rotary table 229 (FIG. 17). Therotary table 229, which supports tank 228, is placed on a movable tablesimilar to the movable table 118 (FIG. 7), to measure the distributionand intensity of the radiation beam in the radiosurgery system, asillustrated in FIG. 7. In the radiation treatment planning currentlyemployed in the prior art, the input sent to the radiation treatmentplanning computerized system is from non-isocentric data (SSD) (sourceto surface distance) which is then converted to isocentric data (SAD).This presents two major problems. First, the conversion algorithms usedfor the conversion are complicated. Second, the results are inaccurate.Additionally, the present invention provides a system having a modulardesign which can be applied to a 1-D (imensional), 2-D and 3-D systems.

Tank 228 can be rotated about the Z axis by a rotary table 229. A firstplurality of rails 235, 236 are secured to the left 237 and right 238sides of the tank 228 (FIG. 17). Linear slide rails (not shown) aremounted in the rails 235 and 236. These linear slide rails arepreferably the linear slide rails manufactured by IKO Nippon ThompsonCompany, LTD. However, other equivalent linear slide rails could also beemployed. Two motors 250 and 252 or similar devices move tank 228 alongrails 235, 236 in upward and downward directions. This motion moves thetank 228 in the Z direction. This construction enables the entire deviceto be rotated about the Z axis by a motor or similar device (not shown).This rotary table 229 positions the system at any desired angle to allowdiagonal and/or transverse scanning by detector 234.

A device 242 moves the vertical arm 243 along guideway 244 by a motor orsimilar device 239. This can be accomplished automatically or manually.This motion along guideway 244 also moves the detector 234 along the Xaxis. The detector or sensor 234 is mounted on a support 240. Thesupport 240 can be moved vertically up and down along the Z axis bymotor 241 (FIGS. 17 and 18) or similar device either automatically ormanually. Motor 241 moves detector 234 vertically. The two motors 250and 252 move the tank 228 vertically along the Z axis. Motors 241, 250,and 252 can be operated simultaneously and in opposite directions sothat the detector 234 will remain stationary. This is accomplished byoperating motor 241 in one direction and both motors 250 and 252 in theopposite direction. This operation permits isocentric scanning of theradiation beam.

By moving the detector 234 along the X and Z axes, scanning isaccomplished transversely and in depth with respect to the radiationbeam and treatment site in an individual, the object being measured. Therotary table 229 permits scanning in the radial and diagonal directionswith respect to the radiation beam and treatment site in an individual,the object being measured. Thus, motions along the X, Y, and Z axesprovide a device and system which can scan in depth, in a radialdirection, in a transverse direction, and in a diagonal direction withrespect to the object being measured.

This operation permits isocentric scanning of the radiation beams. Inthis method the source to the axis (target, probe, radiation detector)distance SAD remains constant. This is a preferred method of treatmentof the patient. This method also permits a direct measurement ofisocentric beams which range from 0.4 cm to 40 cm field sizes. Othermethods of measurement of isocentric radiation beams only allow fieldsizes of 0.4 cm to 6 cm. Non isocentric measurements, on the other hand,can cause significant errors (up to 20%), especially in the small fieldsof sterotactic treatment.

The third embodiment enables measurements of substantially larger fieldsthan the first two embodiments without the use of a large tank of water.This is accomplished by rotating tank 228 up to 90 degrees from a firstposition to a second position. This movement enables detector 234 to bemoved over a substantially larger area without employing a large tank.The use of the thinner tank 228, in the Y direction, on a rotary base,results in a significant reduction in the size of the tank and volume ofwater required to make measurements in large fields. This also resultsin a significant weight savings because of the relative small volume ofwater used: 16 gallons vs. 50 gallons in a conventional tank. Apreferred tank is 35 cm long, 30 cm wide, 40 cm high, and made from anacrylic material.

A fourth embodiment of the present invention is illustrated in FIG. 18.In this embodiment a small stepper motor or similar device 260 issecured to one side of device 242. A track 262 or rod with teeth thatinteract with a gear is secured to the device 242 on the same side asthe motor 260. A controller operates the motor 260 which moves 242 andattached detector 234 in the Y direction, toward and away from the rearwall of tank 128. The motor 260 and be operated in conjunction withmotor 239 to permit the detector 234 to move in a diagonal directionbetween the Y and X axes. Motor 260 can also be operated in conjunctionwith motors 250 and 252 to permit the detector 234 to move in a diagonaldirection between the Z and Y axes.

In a fifth embodiment of the present invention, a treatment table 118having a controlled rotation feature which allows the treatment table tobe rotated around an axis may be utilized in place of motor 254 and itsassociated gear train 256 to rotate the tank of water 128. It should benoted that a single stepper or digital motor having suitable torque maybe utilized in place of the combination of the motor and gear train torotate the tank without departing from the scope of the invention. Inthis method the movement of the X and Y axes are coordinated with therotation of the treatment table to provide the three axes of controlledmovement of the dosemetry probe or sensor 134. The three axes canthereby be controlled to maintain the sensor at a predetermined distancefrom the accelerator for isocentric testing.

All patents and publications mentioned in this specification areindicative of the levels of those skilled in the art to which theinvention pertains. All patents and publications are herein incorporatedby reference to the same extent as if each individual publication wasspecifically and individually indicated to be incorporated by reference.

It is to be understood that while a certain form of the invention isillustrated, it is not to be limited to the specific form or arrangementherein described and shown. It will be apparent to those skilled in theart that various changes may be made without departing from the scope ofthe invention and the invention is not to be considered limited to whatis shown and described in the specification and any drawings/figuresincluded herein.

One skilled in the art will readily appreciate that the presentinvention is well adapted to carry out the objectives and obtain theends and advantages mentioned, as well as those inherent therein. Theembodiments, methods, procedures and techniques described herein arepresently representative of the preferred embodiments, are intended tobe exemplary and are not intended as limitations on the scope. Changestherein and other uses will occur to those skilled in the art which areencompassed within the spirit of the invention and are defined by thescope of the appended claims. Although the invention has been describedin connection with specific preferred embodiments, it should beunderstood that the invention as claimed should not be unduly limited tosuch specific embodiments. Indeed, various modifications of thedescribed modes for carrying out the invention which are obvious tothose skilled in the art are intended to be within the scope of thefollowing claims.

1. A radiation beam analyzer for detecting radiation dosimetry of a beamemitted along an axis from a radiotherapy treatment device comprising: aphantom body formed of a material having a density proximate that of ahuman body; a tank containing said phantom body; at least one dosimetryprobe constructed and arranged to sense photons and electrons, said atleast one dosimetry probe positioned within said dynamic phantom body; aplurality of rails secured to said tank and said dynamic phantom body; arotary table, said tank and said plurality of rails and said secondplurality of rails being positioned on said rotary table; and aplurality of mechanisms incrementally moving said tank and said dynamicphantom body in a substantially vertical, radial, transverse or diagonaldirection relative to a radiation source; the distance between saidradiation source and the axis of a beam emitted from said radiationsource relative to said at least one dosimetry probe being constant;whereby movement of said tank and said phantom body through a series oflocations is carried out so as to provide sufficient data to determinethe proper dose of radiation required for radiotherapeutics.
 2. Theradiation beam analyzer of claim 1 wherein said dosimetry probe is anion chamber.
 3. The radiation beam analyzer of claim 1 wherein saidradiation beam analyzer directly measures radiation from isocentricbeams in a field of approximately 0.4 cm to 40 cm.
 4. The radiation beamanalyzer of claim 1 wherein said movement is isocentric.
 5. Theradiation beam analyzer of claim 1 wherein said radiotherapy treatmentdevice is a linear accelerator.
 6. The radiation beam analyzer of claim1 wherein said dosimetry probe is at least one diode.
 7. The radiationbeam analyzer of claim 1 wherein said rotary table includes a motor anda gear train, said motor and said gear train constructed and arranged toprovide rotation about an axis upon operation of said motor.
 8. Theradiation beam analyzer of claim 7 wherein said rotary table is atreatment table.
 9. A radiation beam analyzer for detecting radiationdosimetry of a beam emitted along an axis from a radiotherapy treatmentdevice comprising: a phantom body formed of a material having a densityproximate that of a human body; a tank containing said phantom body; atleast one dosimetry probe constructed and arranged to sense photons andelectrons, said at least one dosimentry probe positioned within saiddynamic phantom body; a plurality of rails secured to said tank and saiddynamic phantom body; a rotary table, said tank, and said plurality ofrails being positioned on said rotary table; a plurality of mechanismsincrementally moving said tank and said phantom body in a substantiallyvertical, radial, transverse or diagonal direction relative to aradiation source; and a controller connected to and operating saidplurality of mechanisms to move both said tank and said at least onedosimetry probe to maintain the distance between said radiation sourceand the axis of a beam emitted from said radiation source relative tosaid at least one dosimetry probe constant; whereby movement of saidphantom body and said at least one dosimetry probe through a series oflocations is carried out so as to provide sufficient data to determinethe proper dose of radiation required for radiotherapy treatment. 10.The radiation beam analyzer of claim 9 wherein said dosimetry probe isan ion chamber.
 11. The radiation beam analyzer of claim 9 wherein saidradiation beam analyzer directly measures radiation from isocentricbeams in a field of approximately 0.4 cm to 40 cm.
 12. The radiationbeam analyzer of claim 9 wherein said movement is isocentric.
 13. Theradiation beam analyzer of claim 9 wherein said radiotherapy treatmentdevice is a linear accelerator.
 14. The radiation beam analyzer of claim9 wherein said dosimetry probe is at least one diode.
 15. The radiationbeam analyzer of claim 9 wherein said rotary table includes a motor anda gear train, said motor and said gear train constructed and arranged toprovide rotation about an axis upon operation of said motor.
 16. Theradiation beam analyzer of claim 15 wherein said rotary table is atreatment table.
 17. A method of calibrating a radiotherapy treatmentdevice comprising: providing a source of radiation along an axis;providing a phantom body formed of a material having a density proximatethat of a human body; providing a tank containing said phantom body;providing at least one dosimetry probe constructed and arranged to sensephotons and electrons; positioning said at least one dosimetry probewithin said phantom body; providing a plurality of rails secured to saidtank and said phantom body; providing a rotary table; positioning saidtank and said plurality of rails on said rotary table; incrementallymoving said tank and said phantom body in a substantially vertical,radial, transverse or diagonal direction relative to a radiation source;and employing a controller to simultaneously move both said tank andsaid at least one dosimetry probe relative to each other whilemaintaining the distance between a radiation source and the axis of abeam emitted from the radiation source relative to said at least onedosimetry probe substantially constant; whereby movement of said phantombody through a series of locations is carried out so as to providesufficient data to determine the proper dose of radiation required forradiotherapy treatment.
 18. The method of calibrating a radiotherapytreatment device of claim 17 wherein one of said plurality of rails is aZ-axis guideway constructed and arranged to traverse said dosemetryprobe.
 19. The method of calibrating a radiotherapy treatment device ofclaim 17 wherein one of said plurality of rails is a Y-axis guidewayconstructed and arranged to traverse said tank.
 20. The method ofcalibrating a radiotherapy treatment device of claim 17 wherein one ofsaid plurality of rails is a X-axis guideway constructed and arranged totraverse said dosemetry probe.